Faulty fuel gauge?

[CarlosPints]

Hello!

I have a Gen 6 ST 1.8 with a faulty fuel readout and temperature gauge - the former is stuck at around 25% and the latter stays at C (even with the engine running fine!)

The guy I bought it off initially thought it had been a faulty fuel sender (logical thinking on his part) and had that replaced - didn't fix the issue. He then got hold of another Gen 6 instrument cluster and swapped in the gauge motor from the spare to the car's main instrument panel. That didn't work either.

I took out the instrument cluster, checked the main plug connection was securely fastened and tried firing her up again to see if the connector had simply been loose; no luck.

AFAIK the Gen 6 has a single fuse for the entire instrument cluster, and this appears to be fine (the rev counter and speedometer are working as normal but I inspected the requisite fuse regardless - all looks OK).

I figure it absolutely has to be an issue isolated to the instrument cluster given temp and fuel share the same gauge panel on the right (surely it's not a coincidence both are dead?) but I'm running out of troubleshooting ideas. What else do you think I can check to identify the fault and find a fix? Or do I just buy a third instrument cluster and swap out the motors for both the temp and fuel gauges, because the most likely issue is the lad who owned it before me managed to buy a spare cluster that also had dead gauges?

Thanks!